To burn or not to burn: using fire to manage a complex grass ecosystem

Abstract

Grader grass (Themeda quadrivalvis) and Indian blue grass (Bothriochloa pertusa) are among a number of invasive grasses causing significant problems for land managers in northern Australia. These grasses are capable of forming monocultures that reduce grazing animal production and change ecosystem processes such as altering fire behaviour and reducing habitat for native fauna.
In northern Australia, fire is a relatively common part of the ecosystem either by deliberate burning or through uncontrolled wild fire. A study of grader grass and Indian blue grass responses to fire in a conservation setting was undertaken at Undara Volcanic National Park from 2006 to 2013 in an area where the two species were growing together.
Grader grass and Indian blue grass responded differently to fire. Annual fires maintained high levels of grader grass biomass while Indian blue grass biomass slowly declined to near zero. An opposite response occurred where fire was excluded with grader grass biomass slowly declining while Indian blue grass biomass increased significantly. Where periodic burning was undertaken, Indian blue grass increased in the years between fires but rapidly declined in the year following a fire. In contrast, grader grass biomass declined in non-fire years and rapidly increased in the year following a fire. The land management implications of the differential fire responses of grader grass and Indian blue grass are discussed.